1. Field of the Invention
This invention relates to vibratory feeders for conveyors and more particularly to a vibratory feeder that requires less power to operate than prior art feeders.
2. Description of the Prior Art
Vibratory parts feeders are commonly used to move mechanical parts from a feeder bowl or to move material or parts along an elongated trough from a supply point to a discharge point. Such feeders frequently include a base mass that is supported upon the floor or upon a feeder stand by vibration isolators which serve to isolate the feeder from the floor. A frame mass is mounted above the base mass by a plurality of inclined leaf spring sets that enable the frame mass to oscillate in response to an exciter motor. Such exciter motors are commonly of an electromagnetic type that includes a field core and a coil mounted on the base mass and an armature mounted on the underside of the frame mass with an air gap between the armature and the field coil. When an alternating current is supplied to the coil, the armature and frame mass are alternately drawn toward the coil and released, thereby flexing the leaf spring sets. Movement of the frame is always 180 degrees out of phase with respect to movement of the base. This causes the frame mass to oscillate at a predetermined frequency that is determined by the frequency of the current supplied to the coil. Since such feeders include only a base mass and a frame mass, they can be referred to as a two mass vibratory feeder system. One such vibratory parts feeder is shown in the U.S. Pat. No. 3,258,111. When such a two mass system is used, the air gap between the armature and the field core must be slightly larger than the distance that the armature and the field coil move. The power required by the electromagnetic coil is directly proportional to the length of this gap and for large movements of the frame mass and of the attached trough, a considerable amount of power is required.
It is known to provide three mass vibratory systems, such as shown in U.S. Pat. Nos. 2,353,492 issued to O'Connor; 3,786,912 issued to Taylor; 4,117,381 issued to Pereny; and 4,007,825 issued to Spurlin et al.